This separates who sees what. Cloudflare (or any OHTTP gateway) sees who talks to who, but can't see the content. The service sees the content but not who you are/your IP.
You can imagine a lot of threat models where who you talk to isn't sensitive, nor is "someone talked to them about X" but knowing both facts is a risk.
You can imagine a lot of threat models where who you talk to isn't sensitive, nor is "someone talked to them about X" but knowing both facts is a risk.